1. Field of the Invention
The present invention relates to a light-emitting diode (LED) driving semiconductor circuit and a light-emitting diode (LED) driving apparatus including the same. In particular, the present invention relates to a lighting apparatus using the light-emitting diode.
2. Description of the Related Art
In recent years, a LED driving semiconductor circuit and a LED driving apparatus including the same are developed and are put into practical use. A LED driving apparatus of a first prior art is disclosed in JP 2001-313423, (A patent document 1).
In the LED driving apparatus of the first prior art, a voltage boost chopper BUT includes an inductor L, a diode D (a light-emitting diode LED can also serve as the diode D) which is connected to the inductor L in series, and a switching element Q of which one end is connected to a connecting point between the inductor L and the anode of the diode D (in the explanation of the following prior art, reference symbols are those used in the drawings of the patent document 1).
The anode of the light-emitting diode LED is connected to the cathode of the diode D. The light-emitting diode LED is driven by the direct current output of the voltage boost chopper BUT.
The cathode of the light-emitting diode LED is connected to a light-emitting diode current-feedback circuit LFC. The LED driving apparatus of the first prior art controls the control circuit CC of the voltage boost chopper BUT, according to the detected signal of the light-emitting diode current-feedback circuit LFC, so as to average out the current of the light-emitting diode during a time range longer than the period of low-frequency ac current.
The on-control of the switching element Q is done when the inductor L releases energy. The off-control of the switching element Q is done according to the switching current or done when a predetermined time passed after the switching-on.
The other end of the switching element Q is connected to a switching current detection circuit SD. Between the light-emitting diode LED and the ground potential, an inductor current detection circuit LD 2316 is provided.
The above-mentioned circuit configuration provides the LED driving apparatus of the first prior art which achieves the excellent stability of the light-emitting diode current, low power loss, a low input current distortion, and comparatively low cost. However, there is a problem as is described below.
(1) Because of the voltage boost chopper BUT, while the switching device is off, no current flows through the light-emitting diode LED. Therefore, flickering occurs in the brightness of the light emission.
(2) Since a resistor SD and a resistor LD are used for the detection of the current flowing through the switching device Q and the light-emitting diode LED, the power loss by these resistors SD and LD is large. Particularly in the LED lighting apparatus, it is necessary to increase the current applied to the LED. In this case, in such a direct current detection method as in the method using SD and LD, the power loss increases.
(3) Since the input voltage is detected using resistors, the power loss occurs constantly by these resistors for detecting input voltage while the LED driving apparatus is working.
(4) Number of circuit components increases, leaving hindrance to the small-sizing of the LED driving apparatus. Particularly, in case of the bulb type LED lighting apparatus, it is unsuitable.
In order to solve the above-mentioned problem, the present invention purposes to provide a LED driving semiconductor circuit having a simple configuration and a low power-loss, and a LED driving apparatus including the same.
The present invention purposes to provide a LED driving semiconductor circuit, which is capable of controlling the current flowing through the light-emitting diode with a high accuracy responding to the input voltage fluctuation, and an LED driving apparatus including the same.